The present invention pertains to improvements in the field of waste recycling. More particularly, the invention is directed to a method of producing commercially useful materials from waste gypsum boards, such as waste GYPROC (trademark) boards.
Waste gypsum boards coming from demolition and gypsum board factories represent a serious threat to the environment as they accumulate by thousands to hundred thousands of tons in many dumping sites. They retain humidity and thus promote the formation of undesirable mildew. Degradation of the calcium sulfate contained in the waste gypsum boards under the influence of infra-red and ultraviolet radiations causes the generation of H.sub.2 S and SO.sub.2 which contaminate the environment.
Gypsum boards contain calcium sulfate dihydrate, silicon dioxide, cellulosic fibers as well as various metal oxides such as aluminum oxide, calcium oxide, ferric oxide and magnesium oxide. Calcium sulfate dihydrate is known to have liquid absorbing properties, as disclosed for example in U.S. Pat. Nos. 4,163,674 and 4,264,543. However, waste gypsum boards are not suitable for use as absorbents or any other useful products such as fillers for agricultural and horticultural applications.